Photocathodes are the heart of all types of electronic light detection and surveillance systems. One of the most popular of these devices is the image intensifier tube. This device converts a barely visible image and/or a near infrared invisible light image to a very bright visible light image. The photocathode converts the ambient light image to an electronic image which is then amplified by vacuum tube and/or solid state structures. The S-1 photocathode is preferred for intensifier tubes because of its strong response to the near infrared portion of the spectrum, which constitutes the major portion of available radiation in most low level ambient light environments. Commercially available cathodes of this type have a sensitivity of approximately of 25 microamperes/lumen when used on a lime glass and Koval sealing borosilicate glass, which becomes the light transmitting substrate. Narrow band sensitivities of 3 to 3.5 microamperes/lumen are achieved when the above cathode is used with a 2540 filter.